Catheter system for emboli containment

ABSTRACT

A multi-catheter emboli containment system is disclosed which is adapted to provide at least one pair of optimized paths for irrigation and aspiration fluid flow. Through careful design of the cross-sectional area of these paths, the present system is able to be compactly utilized in even the smaller size blood vessels. The catheter system itself is provided with occlusive devices to form an emboli containment chamber in which irrigation and aspiration occur. The catheter system of the present invention provides an improved emboli containment and removal system which can be utilized in a wide range of vessel diameters. The system is easy to use and can quickly and efficiently evacuate the containment chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/650,464 filed May 20, 1996 now abandoned, the entirety ofwhich is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical devices, and, inparticular, to a system of improved irrigation and aspiration cathetersused in the containment and removal of emboli resulting from therapeutictreatment of occlusions within blood vessels.

2. Description of Related Art

Human blood vessels often become occluded or blocked by plaque, thrombi,other deposits, or emboli which reduce the blood carrying capacity ofthe vessel. Should the blockage occur at a critical place in thecirculatory system, serious and permanent injury, and even death, canoccur. To prevent this, some form of medical intervention is usuallyperformed when significant occlusion is detected.

Balloon angioplasty, and other transluminal medical treatments, arewell-known, and have been proven efficacious in the treatment ofstenotic lesions in blood vessels. The application of such medicalprocedure to certain blood vessels, however, has been limited, due tothe risks associated with creation of emboli during the procedure. Forexample, angioplasty is not the currently preferred treatment forlesions in the carotid artery, because of the possibility of dislodgingplaque from the lesion, which can enter the various arterial vessels ofthe brain and cause permanent brain damage. Instead, surgical proceduressuch as carotid endarterectomy are currently used, wherein the artery issplit open and the blockage removed, but these procedures presentsubstantial risks.

Other types of intervention for blocked vessels include atherectomy,deployment of stents, introduction of specific medication by infusion,and bypass surgery. Each of these methods are not without the risk ofembolism caused by the dislodgement of the blocking material which thenmoves downstream. In addition, the size of the vessel may limit accessto the vessel.

Thus, there is a need for a system to contain and remove such emboli.Various devices and methods have been proposed, but none have beenespecially commercially successful. Perhaps this is because a number ofsignificant problems are faced in designing a system which will quicklyand easily, yet effectively, evacuate emboli from a treatment locationwithin a blood vessel. First, the small size of certain vessels in whichsuch therapy occurs is a limiting factor in the design of embolicontainment and removal systems. Vessels as small as 3 mm in diameterare quite commonly found in the coronary arteries, and even certainsaphenous vein graph bypass vessels can also be as small as 3 mm or 4mm; although some can range as high as 7 mm. Certain of the carotidarteries also can be as small as 4 mm in diameter; although, again,others are larger. Nevertheless, a successful emboli removal system mustbe effective within extremely small working areas. The system is equallyeffective in larger vessels, those of 5 mm or more in diameter.

Another obstacle is the wide variety in emboli dimensions. Althoughdefinitive studies are not available, it is believed that emboli mayhave approximate diameters ranging anywhere from tens of micrometers toa few hundred micrometers. More specifically, emboli which areconsidered dangerous to the patient may have diameters as large as 200to 300 micrometers or even larger. Thus, an effective emboli removalsystem must be able to accommodate relatively large embolic particlesand, at the same time, fit within relatively small vessels.

Another difficulty that must be overcome is the limited amount of timeavailable to perform the emboli removal procedure. That is, it will beunderstood that in order to contain the emboli produced as a result ofintravascular therapy, the vessel must be occluded, meaning that noblood perfuses through the vessel to the end organs. Although certainperfusion systems may exist or may be developed which would provideocclusion to emboli while permitting the substantial flow of blood, atpresent, the emboli may be contained only with a complete occlusion asto both blood flow and emboli escapement. Thus, again depending upon theend organ, the complete procedure, including time for the therapeutictreatment as well as exchanges of angioplastic balloons, stents, and thelike, must be completed within just a few minutes. Thus, it would bedifficult to include time for emboli removal as well. This isparticularly true in the larger size vessels discussed above wherein alarger volume results in additional time required for emboli evacuation.

Moreover, it is important that an emboli containment and removal systembe easy to use by physicians, and compatible with present therapeuticdevices and methods. In addition, there are other difficulties whichhave made the successful commercialization of emboli containment andremoval systems thus far virtually unobtainable.

SUMMARY OF THE INVENTION

The present invention advantageously satisfies the need in the prior artby providing a catheter system adapted to provide at least one pair ofoptimized paths for irrigation and aspiration fluid flow. Throughcareful design of the cross-sectional area of these paths, the presentsystem is able to be compactly utilized in even the smaller size bloodvessels. It can also be easily adapted to provide efficient and speedyemboli containment and evacuation in larger size vessels. This system iscompatible with more common therapy devices in widespread use today, andis designed for rapid evacuation and ease of use.

It will be appreciated that, as used herein, the term "catheter" isbroadly used to refer to a number of medical instruments, includingwithout limitation, guidewires, therapy catheters, and the like. Thus,it is important in the present invention that the medical instrumentsused therein cooperate together to define optimized paths for irrigationand aspiration, as set forth herein in more detail.

Thus, in one embodiment of the present system, at least two cathetersare utilized to form and evacuate a treatment chamber. Again, however,it will be appreciated that the term "chamber" refers broadly to atreatment location or site where therapy is performed and embolipossibly produced. The catheters of the present invention telescope onein another in order to form a pair of irrigation and aspiration paths.An outer, larger diameter catheter forms the main body or housing forthe system. An inner, smaller diameter catheter is positioned within thelumen of the outer or main catheter. An optional intermediate, or middlecatheter is positioned over the inner catheter so as to be within thespace formed between the inner and outer catheters. Thus, in thisembodiment, the catheters cooperate to form two irrigation/aspirationpaths: one between the outer catheter and intermediate catheter, and onebetween the intermediate catheter and inner catheter. In anotherembodiment, these paths are formed by the annulus between each pair ofrespective catheters of the present system; although it will beunderstood that, in use, the catheters may not necessarily be positionedconcentric one with another. Therefore, the term "annulus" is used in abroader sense to refer to the path or space between any two catheters.

In addition, rather than being telescoped, the innermost two cathetersmay be placed side-by-side within the main catheter. In this embodiment,less frictional losses are experienced by the fluid as it flows in andout of the irrigation/aspiration paths. Moreover, the intermediatecatheter may take the form of a dedicated irrigation catheter or,conversely, a dedicated aspiration catheter. Likewise, the intermediatecatheter may comprise a therapy catheter which rides over the innercatheter (which itself may take the form as a typical guidewire) to thetreatment site, or the therapy catheter can be built over an aspirationcatheter to provide another embodiment of the intermediate catheter.Since irrigation or aspiration can take place in the path between theinner catheter and the therapy catheter, less time is incurred in theemboli removal process, since the therapy catheter need not be removedin exchange for other types of catheters.

Alternatively, the intermediate catheter can be a single main catheterconfigured to provide both irrigation and aspiration. This catheter hastwo lumens, one of which can extend past the distal end of the catheter.One lumen can be used to provide irrigation, while the other providesaspiration. This dual lumen catheter can be configured such that atleast a portion of the catheter rides over the inner catheter.Alternatively, the catheter can comprise a rheolitic device, or anyother device capable of both treating and aspirating the occlusion. Thiswould eliminate the need for a separate aspiration catheter, thussimplifying the procedure.

In another embodiment, once therapy has been performed, the therapycatheter is removed, and the patient's own blood acts as irrigationfluid. This eliminates the need for a separate irrigation catheter andirrigation fluid. Aspiration can occur through an aspiration catheter,or through the outer catheter. This reduces the time necessary tocomplete the procedure and reduces the number of necessary catheters.

Another aspect of the present invention is that the catheter systemitself is provided with occlusive devices to form an emboli containmentchamber. It will be noted that at least two such occlusive devices areneeded to form a chamber in a straight vessel, while multiple occlusivedevices may be necessary to provide emboli containment in the case of abranching vessel. Again, in this context, the term "occlusive device"makes reference to the blocking or containment of emboli within thechamber, since perfusion systems which provide occlusion to the emboliare within the scope of the present invention. Thus, various types ofocclusive devices such as filters or expandable braids that allowparticles of less than 20 micrometers to pass through while preventingthe passage of larger particles, and including inflatable or expendableballoons such as those which are employed by the present catheter systemor otherwise, are within the scope of the present invention. In onepreferred embodiment, the outer catheter comprises a main catheterhaving an occlusive balloon mounted on the outer diameter thereof. Theocclusive balloon is inflated by means of an inflation lumen formed in awall of the main catheter. The inner catheter comprises what may bereferred to as a guidewire, but which is also hollow to provide aninflation lumen for a second occlusive balloon mounted at the distalsection thereof. This occlusive balloon remains inflated until the guidecatheter crosses the site of the lesion within the vessel. Thus, wheninflated, these two occlusion balloons form an emboli containmentchamber. The inner catheter provides a guidewire for those types oftherapy devices which are in common use. One such catheter for adedicated irrigation/aspiration catheter is positioned over theguidewire to form one of the irrigation/aspiration paths therewith.

Another advantage of the present invention is that the catheters aresized so as to optimize the cross-sectional area of theirrigation/aspiration paths. Thus, a larger range of emboli sizes arecapable of being evacuated. Moreover, irrigation or aspiration ispossible through either path, depending upon the desired conditions orparticular procedure being performed. Thus, the versatility of thepresent system allows, in one embodiment, aspiration to be performedthrough the outer path and irrigation to be provided through the innerpath, or vice versa. It will be noted for clarity that "outer path"refers to that formed between the outer catheter and the intermediatecatheter, while "inner path" refers to that formed between the innercatheter and intermediate catheter.

In another embodiment, the respective irrigation/aspirationcross-sectional areas are designed to balance and optimize flow. Thisbalancing of the path areas not only allows the reversal of irrigationor aspiration, as explained above, but also improves the fluid mechanicsexhibited by the system. That is, the flow of irrigation fluid withinthe vessel can be analogized to fluid flow within a pipe, with theentrance of the pipe being the mouth of the irrigation catheter and theexit of the pipe being the mouth of the aspiration catheter; it is theflow into the chamber versus the flow out of the chamber that createsthe pressure within the chamber. Thus, a differential in pressure at themouths of the irrigation and aspiration catheters will generate a flowrate used to evacuate the containment chamber. However, since flow ratevaries with the product of fluid velocity in the cross-sectional area,for steady flow rate, it would be observed that decreases in thecross-sectional area of one of the irrigation/aspiration paths willproduce an increase in fluid velocity. Since local pressure varies withthe square velocity, such a reduced path cross-sectional area couldproduce an excessive pressure which may damage the vessel. Thus, it isdesirable that local pressures in the vessel not exceed about 1.5atmospheres (e.g., less than about 50 psi). In addition to possibledamage, excessive pressures may simply cause the vessel to expandwithout resulting in any advantageous increase in flow rate. Thus, byoptimizing the respective areas of the irrigation/aspiration paths,these parameters can be maintained within tolerable limits.

Increases in internal or local pressures also require substantialincreases in external pressures. That is, in order to maintain thedesired flow rates necessary to quickly and efficiently evacuate thecontainment chamber, as the cross-sectional area of theirrigation/aspiration paths are reduced, a greater change in pressure(Δp) is required to generate sufficient fluid velocity. Taking intoconsideration the frictional losses in the system, extremely high Δp'smay be required. Thus, it is important to maintain a balanced system sothat excessive internal pressures are not produced, which may damage thevessel. Such pressures may also have the effect of causing a leak in thechamber.

Thus, the present invention provides a catheter system, comprising ahollow inner catheter having an occlusion device mounted on the distalend. At least a portion of an intermediate catheter is positioned overthe inner catheter to create an inner fluid pathway for irrigation oraspiration. The intermediate catheter is slidable to a location proximalto the occlusion device on the inner catheter. A main catheter sized toreceive the intermediate catheter such that an outer fluid pathway isformed therebetween for irrigation or aspiration. The main catheter alsohas an occlusion device mounted on its distal end which cooperates withthe occlusion device on the inner catheter to form a chambertherebetween. The main catheter has an irrigation/aspiration port topermit irrigation or aspiration through its lumen. In one preferredembodiment, irrigation fluid is provided through the inner pathway andaspiration pressure is provided through the outer pathway.

The inner catheter is preferably a guidewire. The intermediate cathetercan be an irrigation catheter, an aspiration catheter, a combinedirrigation/aspiration catheter, or a therapy catheter, such as a drug;delivery catheter, a laser, an ultrasound device, a thrombectomycatheter, a rheolitic device, a stent-deploying catheter, or any of anumber of devices. The therapy catheter can be, for example, a balloonangioplasty catheter. Inflatable balloons can also be used as theocclusion devices on the inner and main catheters. To inflate theballoon, the main catheter can further comprise an inflation lumenlocated in the wall of the catheter in fluid communication with theinflatable balloon. The intermediate catheter can have both a main lumenand a separate lumen adjacent the main lumen sized to received the innercatheter slidably therein. The separate lumen can have a slit in anoutside wall for insertion and removal of the inner cathetertherethrough.

To fit in small blood vessels, it is preferred that the main catheterhas an outer diameter of less than 5 mm. To provide efficient clearanceof the emboli containment chamber, the inner pathway and the outerpathway should have an opening at their distal ends which act to balancefluid flows. In preferred embodiments, the inner pathway and the outerpathway each have an opening allowing the passage of particles of about20 micrometers, up to those at least about 500 micrometers in diameter.

The system can include at least one additional inner catheter having anocclusion device mounted on its distal end sized to fit slidably withinthe intermediate catheter. This system can be used within branchingblood vessels where more than one branch must be occluded to create anisolated chamber.

Accordingly, the catheter system of the present invention provides animproved emboli containment and removal system which can be utilized ina wide range of vessel diameters, including extremely small ones. Thesystem is easy to use and can quickly and efficiently evacuate thetreatment chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the catheter system of the presentinvention illustrating the manner in which an emboli containment chamberis formed.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1illustrating schematically one embodiment of the irrigation andaspiration paths which are formed by the catheter system of presentinvention.

FIG. 3 is a side view of the main catheter for use in the presentinvention.

FIG. 4 is a cross-sectional view of the main catheter taken along line4--4 of FIG. 3.

FIG. 5 is a cross-sectional view of the main catheter taken along line5--5 of FIG. 3.

FIG. 6 is a side view of an over-the-wire irrigation or aspirationcatheter for use in the present invention.

FIG. 7 is a side view of at single operator irrigation catheter for usein the present invention.

FIGS. 8 through 10A are cross-sectional views of the single operatorcatheter taken along lines 8--8, 9--9 and 10A--10A of FIG. 7.

FIG. 10B is a cross-sectional view of the single operator catheterinserted within the main catheter, illustrating schematically the innerand outer paths which are formed by the catheter system of presentinvention.

FIG. 11 is a side view of an over-the-wire aspiration catheter for usein the present invention.

FIG. 12 is a cross-sectional view of the over-the-wire aspirationcatheter taken along line 12--12 in FIG. 11.

FIG. 13 is a cross-sectional view of the over-the-wire aspirationcatheter taken along line 12--12 in FIG. 11, showing a guidewireinserted therethrough.

FIG. 14 is a side view of a single operator aspiration catheter for usein the present invention.

FIG. 15 is a cross-sectional view of the single operator aspirationcatheter taken along line 15--15 of FIG. 14.

FIG. 16 is a side view of an inner catheter for use in the presentinvention.

FIG. 17 is a is a partial cross-sectional view of the inner cathetertaken along line 17--17 of FIG. 16.

FIGS. 18A-H illustrate the use of the catheters of the present inventionin emboli containment treatment procedures.

FIG. 19 is a graph illustrating the exponential trend of fluid flowversus pressure in the emboli containment chamber.

FIG. 20 is a graph illustrating the effect of irrigation and aspirationpressures on flow rate within the emboli containment chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a system of improved irrigation andaspiration catheters used in the treatment of occlusions within bloodvessels and emboli containment. The apparatus of the present inventionare adapted for use in the treatment of an occlusion in a blood vesselin which the occlusion has a length and a width or thickness which atleast partially occludes the vessel's lumen. It is to be understood that"occlusion" as used herein, includes both complete and partialocclusions, stenoses, emboli, thrombi, plaque, and any other substancewhich at least partially occludes the lumen of the blood vessel.

Emboli Containment and Removal

Referring to FIG. 1, there is shown a schematic illustration of thecatheter system of the present invention and the manner in which itforms an emboli containment chamber for efficient emboli removal. Thecatheter system, in this embodiment, comprises a three-catheter system,including an outer or main catheter 20, an intermediate catheter 22, andan inner or guidewire catheter 24. This catheter system is shownschematically inserted within a relatively small vessel having adiameter d. As set forth above, the diameter d of the vessel may be assmall 3 mm to 4 mm; although the present system can be efficientlyutilized within vessels of larger diameter. An emboli containmentchamber is formed between the outer 20 and inner 24 catheters, each ofwhich in the preferred embodiment are provided with inflatable occlusionballoons 26 and 28. As noted above, the present invention is compatiblewith other types of occlusive devices, including those which permitperfusion and those which have other deployment mechanisms, such asfilters, braids and the like. The present system is also compatible withcontainment chambers of variable length. Chambers of longer lengthscontain a large volume of fluid and, thus, increase the time for embolievacuation and/or increase the pressure differential (Δp) required toachieve desirable evacuation flow rates. Thus, containment chambers inthe range of about 0.3 cc to 30 cc are preferable.

Although FIG. 1 illustrates the present catheter system deployed withina straight vessel, it will be understood that the principles of thepresent invention also include other vessel configurations, includingbranches vessels. In such cases, a third or even additional occlusivedevices may be used in order to contain the emboli and form a workingchamber. Such occlusive devices could be mounted on additional innercatheters similar to the one illustrated in FIG. 1, or on a single innercatheter having itself two branches, or otherwise. FIG. 1 illustrates animportant feature of the present invention in which the catheters 20,22, 24 are telescoped within one another. Thus, the inner catheter 24 isrelatively small in outer diameter and fits within the inner diameter ofthe intermediate catheter 22 and can, in some applications, serve as aguidewire therefor. Likewise, the outer diameter of the intermediatecatheter 22 fits within the inner diameter of the outer or main catheter20. The catheters 20, 22, and 24 thus form inner and outer pathways, 30and 32 between the inner 24 and intermediate 22 catheters and theintermediate 22 and outer 24 catheters, respectively. It is throughthese pathways 30, 32 that irrigation or aspiration may be performed.Advantageously, in the present system, irrigation can be performedthrough the inner pathway 30 and aspiration through the outer pathway32, or vice versa. As explained below in more detail, irrigation refersto the injection of fluid through one of the pathways into thecontainment chamber in order to generate an evacuation flow rate. Fluid,together with emboli, are evacuated through the other pathway, beingassisted by the aspiration pressure which is in reality a suction ornegative pressure. It is this pressure differential over some lengthwithin the chamber which generates the evacuation fluid flow.

As merely one example, irrigation fluid could be supplied at onepressure through the irrigation pathway as indicated by the small arrowsin FIG. 1. Due to the pressure differential in the chamber, fluid beginsto flow toward the outer pathway, being assisted by the negativeaspiration pressure. Thus, emboli in the chamber are swept through theouter pathway indicated by the arrows. Accordingly, FIG. 1 illustratesone catheter arrangement of the present invention in which the catheters20, 22, 24 are telescoped one inside the other; although the principlesof the present invention apply equally well to other nontelescopedcatheter configurations. Also, as noted above, other types of cathetersmay be used in connection with the present system. FIG. 2 illustrates across-sectional view of the present catheter system taken along lines2--2 of FIG. 1, and illustrates in further detail relativecross-sectional dimensions of the inner and outer pathways. However, itwill be noted that FIG. 2 is schematic in the sense that it illustratesthe inner 24 and intermediate 22 catheters positioned at the bottom ofthe lumen of the outer catheter 20. This is for ease of illustrationonly, as it will be understood that in actual practice the positions ofthe various catheters 20, 22, 24, relative one to another may vary dueto pressures, flow rates, etc. The catheters 20, 22, 24 of the presentsystem are designed so as to compactly fit within even small diametervessels and at the same time optimize the cross-sectional areas of theinner and outer pathways. This design criteria, for a given flow rate,can be expressed as follows: ##EQU1## where: Q=flow rate

Dp=pressure differential between the proximal and distal ends of thecatheter

D=net diameter of the catheter

L=the overall length of the catheter

μ=the viscosity of the fluid

128=constant factor

Thus, when a particular desired flow rate is known, the foregoingequation can be solved for D to give an optimized inner diameter of theintermediate catheter 22 when empty, or an equivalent diameter when theinner diameter is partially occluded by, for example, the innercatheter. It will be noted that the diameter of the intermediatecatheter 22 is perhaps the more sensitive design parameter since, as itincreases or decreases the cross-sectional areas of the inner and outerpathways increases and decrease, respectively. Furthermore, the otherparameters in the equation are often given, including the externalpressure differential, the length of the intermediate catheter 22 (whichis tropically about 100-120 cm) and the viscosity of the fluid. As forthe desired flow rate, it will be understood that merely one flushing ofthe containment chamber may not be sufficient to remove all emboli. Thisis because of the relatively high viscosity of the patient's blood inthe chamber and the inertia of the emboli which must be overcome. Also,as set forth above, some emboli are relatively large in diameterrequiring several flushes. Thus, preferably, the flow rate will be suchthat the fluid in the containment chamber is changed at least abouttwice within a two- or three-minute period, while maintaining the localpressure in the chamber within a safe range (less than about 50 psi).Preferably, the fluid will be changed as many as five times or morewithin a minute in order to reduce the overall treatment time inconnection with these procedures.

It will be understood that FIG. 2 illustrates an ideal condition inwhich size of the openings of the inner and outer pathways aremaximized. As this illustration does not always represent actualconditions, emboli size must be taken into consideration. Thus, themaximized opening for the inner and outer pathways (ip_(m) and op_(m))should be at least about 150 micrometers and more preferably about 1000micrometers. Thus, in the minimum state, where all of the catheters 20,22, 24 are approximately concentric with one another, ip_(m) and op_(m)will range between about 250 and 500 micrometers. Thus, good evacuationperformance should still be attainable.

In one embodiment of the present system, described below in more detailin connection with an irrigation and aspiration study, a catheter systemfound to be suitable comprised an outer catheter 20 with an innerdiameter of 0.086" and an intermediate catheter 22 with inner and outerdiameters of 0.048" and 0.054", respectively. The inner catheter 24comprises a guidewire of typical outer diameter of about 0.014" but canbe as large as 0.038". Converting these dimensions to micrometers yieldsa total inner diameter of the outer catheter 20 of about 2200micrometers, an outer diameter of the inner catheter 24 of about 355micrometers, and a wall thickness of the intermediate catheter 22 ofabout 150 micrometers. This leaves a maximum inner pathway opening(ip_(m)) of about 770 micrometers and the maximum outer pathway opening(op_(m)) of about 800 micrometers. This will be sufficient to removeeven larger sized emboli. This example also illustrates a cathetersystem configuration in which the respective cross-sectional areas ofthe inner and outer pathways are similar, thus yielding a balancedpressure differential condition in the containment chamber. Byeliminating the use of the intermediate catheter, as explained below,the opening of the outer pathway can be increased even more.

Catheter Construction

Outer Catheter

FIG. 3 illustrates a side view of a catheter which can be used as theouter catheter of the present system. Catheter 110 generally comprisesan elongate flexible tubular body 116 extending between a proximalcontrol end 112 and a distal functional end 114. The tubular body 116has a main lumen 130 which extends between the ends 112 and 114. Themain lumen 130 terminates in a proximal opening 123 and a distal opening127. A smaller inflation lumen 132, configured in a side-by-siderelationship with the main lumen 130, extends along the length of thetubular body 116, and terminates within an occlusion balloon 126 mountedon the distal end 114 of the catheter 110, as described below. Theinflation lumen 132 is in fluid communication with the occlusion balloon126, such that fluid passing through the inflation lumen 132 may be usedto inflate or deflate the balloon 126. The infaltion lumen can terminateat its proximal end at one of the ports 122, 124 on the catheter 110.

The tubular body 116 must have sufficient structural integrity, or"stiffness," to permit catheter 110 to be advanced through vasculatureto distal arterial locations without buckling or undesirable bending oftubular body 116. However, it is also desirable for tubular body 116 tobe fairly flexible near its distal end 114, so that the tubular body 116may be navigated through tortuous blood vessel networks. Thus, in onepreferred embodiment, the body 116 is made to have variable stiffnessalong its length, with the proximal portion of the body 116 being lessflexible than the distal portion of the body 116. Advantageously, atubular body 116 of this construction enables a clinician to more easilyinsert the catheter into blood vessel networks difficult to reach bycatheters having uniform stiffness. This is because the stiffer proximalportion provides the requisite structural integrity needed to advancethe tubular body 116 without buckling, while the more flexible distalregion is more easily advanced into and through tortuous blood vesselpassageways.

In one preferred embodiment, variable stiffness along the length of thetubular body 116 is achieved by forming a polymeric tubular body 116which incorporates a reinforcement along its length. Such reinforcementcan be a braid or coil formed of various metals or polymers. The body116 may be provided with a reinforcement incorporated into its wallstructure. To achieve variable stiffness, the proximal region of thecatheter 110 can be provided with greater reinforcement than the distalregion.

The precise density of the braiding or pitch of the coil provided to theproximal and distal regions can be varied considerably at the point ofmanufacture, such that catheters having a variety of differentflexibility profiles may be created. Moreover, the braid density or coilpitch may be varied within the various catheter regions, by providing areinforcement that has a density or pitch gradient along its length.

A variety of different materials, known to be ductile and shapeable intofine wires, may be used to form the reinforcement, such as variouspolymers, stainless steel, gold or silver plated stainless steel,ELGILOY, platinum or nitinol. The reinforcement may be introduced intothe structure of the catheter body 116 through conventional catheterforming techniques. Moreover, any of a variety of different polymericmaterials known by those of skill in the art to be suitable for catheterbody manufacture may be used to form the tubular body 116. Differentmaterials might also be combined to select for desirable flexibilityproperties.

Also, although the tubular body 116 has been described in the context ofhaving two regions of differing flexibility, it will be readilyappreciated by those of skill in the art that three or more regions ofdiffering flexibility may easily be provided, by adapting the teachingscontained herein.

A control manifold 119 is provided at the proximal end 112 of thecatheter 110. The control manifold 119 is generally provided with anumber of ports to provide access to the catheter lumen 130. Forexample, for the embodiment depicted in FIG. 3, the control manifold 119is provided with a catheter end-access port 122 and a catheterside-access port 124, to provide an introduction point for the insertionof other catheters into the lumen 130. Ports 122 and 124 are preferablyprovided with standard Touhy Borst connectors, although other types ofconnectors may be used. An inflation port 118, in fluid communicationwith the small inflation lumen 132, is further provided on the manifold119 for attachment of devices to inflate or deflate the balloon 126. Themanifold 119 is also provided with an irrigation/aspiration port 120which is in fluid communication with the lumen 130, for attachment ofdevices to provide irrigation fluid or aspiration pressure. Otherembodiments of the main catheter 110 may feature more or less ports,depending upon the number of lumen in the catheter and the desiredfunctionalities of the catheter.

The manifold 119 is preferably formed out of hard polymers or metals,which possess the requisite structural integrity to provide a functionalaccess port to the catheter lumen, such as for balloon inflation ordelivery of irrigation fluid and/or aspiration pressure. In onepreferred embodiment, the manifold 119 is integrally formed out ofpolycarbonate. Of course, any suitable material may be used to form themanifold 119.

The manifold 119 is attached to the tubular body 116 so that the variousports are placed in communication with the appropriate lumen, asdescribed above in connection with FIG. 3. Preferably, a strainrelieving connector 111 is used to join the manifold 119 to the tubularbody 116. For the embodiment depicted in FIG. 3, the strain relievingconnector 111 consists of a length of flexible polymeric tubing, such aspolyethylene terephthalate (PET). The tubular body 116 is inserted inone end of the strain relieving connector 111, and the other end of thestrain relieving connector 111 is inserted into the manifold 119. Asuitable adhesive, such as a cyanoacrylate, may be used to bond themanifold 119 to the strain relieving connector 111. Adhesives may alsobe used to bond the strain relieving connector 111 to the tubular body116, or alternately, conventional heat bonding, as known to those ofskill in the art, may be used to attach the tubular body 116 to thestrain relieving connector 111.

Although not required, the interior surface of the lumen 130 may beprovided with a liner 135 formed of a lubricous material, to reduce thefrictional forces between the lumen surface and the catheters which areinserted into the lumen 130. In one preferred embodiment, the liner 135is formed out of polytetrafluoroethylene (PTFE). Materials other thanPTFE, which are biocompatible, fairly flexible, and easily mounted toother polymeric materials of the type used to form catheter tubularbodies, may also be used to form the liner 135.

To minimize the outer diameter of the tubular body 116, it is preferablethat the inflation lumen 132 be as small as possible in accordance withits function. That is, the inflation lumen 132 is preferably no largerthan required to provide sufficient fluid to the occlusion balloon 126for rapid inflation, or so that fluid may be quickly withdrawn from theballoon 126 during deflation. For compliant expansion balloons of thetype described below, inflation lumen diameters of from about 0.006inches to about 0.020 inches are satisfactory, with a diameter of about0.010 inches being optimal.

Furthermore, in one embodiment, as illustrated in FIGS. 3-5, the outerdiameter of the tubular body 116 just proximal to the balloon 126 isminimized by providing an inflation lumen 132a with an ovalcross-sectional configuration, as illustrated in FIG. 5. Preferably,this inflation lumen 132a has an oval cross-sectional configurationwhich extends proximally from the proximal end of the balloon 126 by adistance of at least 0.1 cm, more preferably 1 cm, and optimally by adistance equal to the length of the tubular body. For ease ofmanufacturing, the cross-sectional configuration of the lumen 132 atpoints further proximal to the balloon 126 may be generally circular, asillustrated in FIG. 4. Where the lumen configuration differs fromproximal to distal end, as illustrated in FIGS. 4 and 5, a region oftransition 133 is provided wherein the lumen configuration changes fromcircular to oval.

As illustrated in FIG. 3, an inflatable balloon 126 is mounted on thedistal end 114 of the catheter 110. In most applications where thecatheter 110 is to be used in an emboli containment treatment procedure,the inflatable balloon 126 will function as an occlusion balloon, toprevent blood from passing through the blood vessel distal of theballoon 126. Thus, the inflatable balloon 126 is preferably able toexpand to fit a variety of different blood vessel diameters.Accordingly, it is preferred that the inflatable balloon 126 have acompliant expansion profile, tending to increase in radial diameter withincreasing inflation pressure. To achieve this, the balloon 126 may bemade out of materials which impart such expansion characteristics,including elastomeric materials such as latex or irradiatedpolyethylene. In one preferred embodiment, the inflatable balloon 126 isformed out of a material comprising a block copolymer ofstyrene-ethylene-butylene-styrene, sold under the trade name C-FLEX.Further details as to balloons of this type are disclosed in U.S. Pat.No. 5,868,705, the entirety of which is incorporated by reference.

The inflatable balloon 126 can be placed in fluid communication with thelumen 132a via a fill hole (not shown) extending through the tubularbody 116 within the balloon 126, such that fluid may be introduced intothe lumen 132 through an inflation port 118 to inflate the balloon 126.Alternately, the lumen 132a may terminate within the balloon 126, toprovide the requisite fluid communication. The balloon 126 may beattached to the tubular body 116 by any suitable manner known to thoseof skill in the art, such as adhesives or heat bonding.

Intermediate Catheter

FIG. 6 is a side view of an irrigation or aspiration catheter 140 whichmay be utilized as the intermediate catheter. It should be understoodthat when an irrigation catheter is used for the intermediate catheter,aspiration occurs through the outer pathway between the intermediate andmain catheters, while irrigation occurs through the inner pathway. Whenan aspiration catheter is used as the intermediate catheter, aspirationoccurs through the inner pathway between the intermediate and maincatheters, while irrigation occurs through the outer pathway. Irrigationfluid under pressure is supplied at the proximal end of the catheter 142and delivered into the containment chamber through the side holes 146and through the distal end of the chamber 144. Alternatively, aspirationor negative pressure can be provided at the proximal end of the catheter142 and fluid and debris aspirated through the side holes 146 and thedistal end of the catheter 144. The catheter 140 may be about 125 cm inlength and constructed from a plastic material such as HYTREL tubing,high density polyethylene (HDPE) or PEBAX (Atochem, France). In order toachieve a softer distal section, the durometer of the tube 148 materialis reduced in that area to about 55 whereas that of the proximal section142 is higher, such as about 80. The distal opening is preferably about0.040", and the outer diameter is preferably about 0.065". Proximalvalves and fittings which are well known in the art can be mounted onthe irrigation catheter 140 of FIG. 6. This catheter can be of eitherover-the-wire (as shown) or single operator design, as explained in moredetail below.

FIGS. 7-10 illustrate another type of irrigation or aspiration catheter230 which can be used as the intermediate catheter of the presentsystem. In the case of the irrigation catheter, irrigation is throughthe inner pathway and aspiration is through the outer pathway. If thecatheter is used for aspiration, aspiration is through the inner pathwayand irrigation is through the outer pathway. As shown in FIGS. 7-10, thecatheter 230 has an adaptor 232 on its proximal end. This singleoperator catheter 230 further comprises a long tubular body 236 having adistal end 238. The distal tip 238 can include a radiopaque marker toaid in locating the tip 238 during insertion into the patient, and ispreferably soft to prevent damage to the patient's vasculature. At thedistal end of the shaft 238, an inner catheter lumen 240 is attached.This lumen 240 provides a separate lumen, apart from the main lumen 242of the catheter 230, for the insertion of the inner catheter. The innerdiameter of the inner catheter lumen ranges from about 0.016" to about0.020" for use with a 0.014" inner catheter system. In a preferredembodiment, the inner diameter of the lumen is about 0.019 in. Thisinner catheter or guidewire lumen can be as short as 5 cm, but canextend 30 cm or longer in a proximal direction. During delivery of thecatheter 230, the proximal end of the inner catheter is inserted intothe distal end of the inner catheter lumen 240, and the lumen 240 isslidably advanced over the inner catheter. Only a short segment of thesingle operator catheter 230 rides over the inner catheter, and theinner catheter remains in the lumen 240 and does not enter the mainlumen 242 of the catheter 230.

Although the inner catheter lumen 240 is shown in FIG. 7 as beinglocated only on the distal end 238 of the shift of the catheter 236, thelumen 240 can also be made to extend the entire length of the shaft 236if desired. In both embodiments, the main lumen 242 is advantageouslyleft completely unobstructed to provide more efficient irrigation oraspiration. The inner catheter lumen 240 can also include a slit 241 orweakened area in the outside wall of the lumen 240 along the entirelength of the lumen 240 to facilitate faster and easier insertion andremoval of the inner catheter through the side wall of the lumen 240. Byinserting and removing the inner catheter through the side wall of thelumen 240 on the catheter 236, the need to remove adapters andattachments from the proximal end prior to slidably advancing orremoving the catheter 236 over the inner catheter is eliminated. Itshould be understood that this slit 241 or weakened area through whichthe inner catheter can be inserted and removed can exist on theintermediate catheter regardless of whether the catheter is used forirrigation, aspiration, therapy or some other purpose.

FIG. 10A is a cross-sectional view of a single operator intermediatecatheter 252 positioned within the main catheter 250. The separate lumen254 adapted to receive the inner catheter is positioned adjacent thelumen of the intermediate catheter 252. It should be understood thatthis positioning will occur when any single operator intermediatecatheter is used. FIG. 10A illustrates schematically the inner (IP) andouter pathways (OP) for irrigation and aspiration which are formed bythe catheter system of the present invention when a single operatorintermediate catheter is used.

Another embodiment of an aspiration catheter suited for use as theintermediate catheter in the present invention is illustrated in FIGS.11-13. The catheter 260 includes an adaptor 262, preferably a femaleluer adaptor, at its proximal end. The catheter 260 further includes anaspiration port 264 to which a source of negative pressure is attached.The aspiration catheter further comprises a long tubular body 266 havinga distal end 268. The distal tip 268 can include a radiopaque marker toaid in locating the tip 268 during insertion into the patient, and ispreferably soft to prevent damage to the patient's vasculature. Theaspiration catheter is preferably about 145 cm in length, although thislength can be varied as desired.

As seen in FIG. 12, the catheter body 266 is hollow, with an internaldiameter ranging from about 0.020" to about 0.050". Preferably, theinner diameter is about 0.045". During insertion of the aspirationcatheter 260, the proximal end of the inner catheter 270 is insertedinto the distal end of the aspiration catheter 268, and the aspirationcatheter 260 is slidably advanced over the inner catheter 270, which ispositioned inside the hollow lumen 272 of the aspiration catheter 260.The position of the inner catheter 270 relative to the body of theaspiration catheter 266 is illustrated in FIG. 13, but of course, canvary. For this type of aspiration catheter 260, a very long innercatheter 270, generally around 300 cm in length, is used to facilitatethe insertion of the aspiration catheter 260.

FIGS. 14-15 illustrate another embodiment of an aspiration catheter 250suitable for use as an intermediate catheter in the present invention.This catheter 280 comprises an elongate shaft 282 with a lumen 284 foraspiration. At the distal end 288, a separate inner catheter lumen 286is positioned adjacent the main aspiration lumen 284. Again, this lumen286 provides a separate lumen, apart from the main lumen 284 of thecatheter 280, for the insertion of the inner catheter. This innercatheter or guidewire lumen 286 can be as short as 5 cm, but can extend30 cm or longer in a proximal direction. During delivery of the singleoperator aspiration catheter 280, the proximal end of the inner catheteris inserted into the distal end of the inner catheter lumen 286, and thelumen 286 is slidably advanced over the inner catheter. Only a shortsegment of the single operator aspiration catheter 280 rides over theinner catheter, and the inner catheter remains in the lumen 286 and doesnot enter the aspiration lumen 284 of the catheter 280. Again, the lumen286 can have a slit (not shown) or weakened area in a side wall tofacilitate insertion and/or removal of the inner catheter through theside wall of the lumen.

If desired, a rheolitic device such as the ANGIOJET thrombectomycatheter available from Possis Medical Inc., Minneapolis Minn. can beused. This device acts as both a therapy catheter and anirrigation/aspiration catheter. The device breaks up the thrombus orother occlusion and removes it. This eliminates the need to provideseparate catheters for these functions. Thus, the term "aspirationcatheter" includes rheolitic devices, thrombectomy devices and anydevice which creates an area of fluid turbulence and uses negativepressure to aspirate fluid and debris, and includes devices which createa venturi effect within the vessel.

Alternatively, a single catheter having two separate lumens can be usedto provide both irrigation and aspiration. The dual lumen catheter canbe configured to be over-the-wire, or of single operator design.Preferably, one lumen extends past the distal end of the catheter sothat the opening of one lumen is spaced some distance apart from theopening of the second lumen. Thus, irrigation occurs some distance awayfrom aspiration.

In another embodiment, a combined aspiration/therapy catheter can beused. For example, an angioplasty balloon can be attached to the distalend of an aspiration catheter. Alternatively, the aspiration cathetercan be designed to deploy a stent within the occluded vessel, or thecatheter could include an atherectomy device on its distal end. Theaspiration and therapy devices are therefore delivered into the bloodvessel together.

In the catheters of the present invention, the elongate catheter shaftmust have sufficient structural integrity, or "stiffness," to permit thecatheter to be pushed through the vasculature to distal arteriallocations without buckling or undesirable bending of the body. It isalso desirable, however, for the catheter body to be fairly flexiblenear its distal end, so that the tubular body may be navigated throughtortuous blood vessel networks. Thus, the tubular body of the cathetercan be formed from a polymer such as polyethylene, or PEBAX made to havevariable stiffness along its length, with the proximal portion of thetubular body being less flexible than the distal portion of the body.Advantageously, a tubular body of this construction enables a user tomore easily insert the tubular body into vascular networks difficult toaccess using conventional catheters of uniform stiffness. This isbecause the stiffer proximal portion provides the requisite structuralintegrity needed to advance the catheter without buckling, while themore flexible distal region is more easily advanced into and throughtortuous blood vessel passageways.

Inner Catheter

As shown in FIGS. 16-17, the inner catheter apparatus 310 can generallybe comprised of four communicating members including an elongatedtubular member 314, a balloon member 316 and a core-wire member 320 anda coil member 322. The catheter apparatus 310 is preferably providedwith an outer coating of a lubricous material, such as TEFLON.

The body tubular member 314 of the catheter apparatus 310 is in the formof hypotubing and is provided with proximal and distal ends 314A and314B and as well as an inner lumen 315 extending along the tubularmember 314. The balloon member 316 is coaxially mounted on the distalend 314B of the tubular member 314 by suitable adhesives 319 at aproximal end 316A and a distal end 316B of the balloon member 316 as inthe manner shown in FIG. 17. The core-wire member 320 of the catheter310 may be comprised of a flexible wire 320. The flexible wire 320 isjoined by soldering, crimping or brazing at a proximal end 320A of theflexible wire 320 to the distal end 314B of the tubular member 314 as inthe manner show in FIG. 17.

Preferably, the proximal end 320A of the flexible wire 320 has atransverse cross sectional area substantially less than the smallesttransverse cross-sectional area of the inner lumen 315 of the tubularmember 314. In the preferred embodiment, the flexible wire 320 tapers inthe distal end 320B to smaller diameters to provide greater flexibilityto the flexible wire 320. However, the flexible wire may be in the formof a solid rod, ribbon or a helical coil or wire or combinationsthereof.

As shown in FIG. 17, the distal end 320B of the flexible wire 320 issecured to a rounded plug 318 of solder or braze at the distal end 322Bof the coil member 322. The coil member 322 of the catheter 310 may becomprised of a helical coil 322. The coil member 322 is coaxiallydisposed about the flexible wire 320, and is secured to the flexiblewire 320 by soldering or brazing at about the proximal end 320A of theflexible wire 320 as in the manner shown in FIG. 17. The balloon member316 is preferably a compliant balloon formed of a suitable elasticmaterial such as a latex or the like. The flexible coil 322 ispreferably formed of a radiopaque material such as platinum or gold. Theflexible core-wire 320 and the tubular member 314 are preferably formedof a nickel-titanium alloy or stainless steel.

The catheters of the present invention are preferably provided with acoating on the outer surface, or on both the inner and outer surfaces.Suitable coatings include hydrophilic, hydrophobic and antithrombogeniccoatings. Examples include heparin and TEFLON. These coatings can beapplied using methods well known in the art.

Additional details relative to the catheters described above are foundin copending applications entitled CATHETER FOR EMBOLI CONTAINMENT, Ser.No. 08/813,023, ASPIRATION CATHETER, Ser. No. 08/813,808, and HOLLOWMEDICAL WIRES AND METHODS OF CONSTRUCTING SAME, Ser. No. 08/812,876, allfiled Mar. 6, 1997, and U.S. Pat. No. 5,868,705, all of which are herebyincorporated by reference.

Fluid Mechanics of Irrigation/Aspiration

In order to understand the design criteria of the catheter system of thepresent invention, it is useful to have some understanding of the fluidmechanics of the system. The effect of the pressure differential betweenthe irrigation and aspiration openings on the emboli containment chamberwas first studied. It was confirmed that as the pressure differentialincreased, the flow rate in the chamber increased exponentially.

Some preliminary studies demonstrated that the fluid flow through theirrigation catheter into the chamber then out through the aspirationcatheter could be represented by equations for fluid flow in pipes. Thebasic equation for incompressible fluid flow in a pipe is based onBernoulli's equation for steady state flow of inviscid, incompressiblefluids:

    p.sub.1 +1/2ρV.sub.1.sup.2 +γZ.sub.1 =p.sub.2 +1/2ρV.sub.2.sup.2 +γZ.sub.2

where p=pressure, ρ=density, V=velocity, γ=specific weight, andZ=elevation. When fluid flows in a pipe or, in this case theirrigation/aspiration system within the containment chamber, thebehavior of the fluid can be described by the equation: ##EQU2## where Kis the resistance coefficient and the fluid velocity V can be expressedin terms of fluid flow (Q) by the equation V=Q/A where A=cross sectionalarea. Therefore for a given irrigation/aspiration system K, A and ρ canbe assumed to be constant, indicating that the square of the fluidvelocity is proportional to the pressure differential between theirrigation and aspiration pressures.

The results of the initial testing clearly showed that the fluid flowthrough the system did behave as predicted and proved that as the changein pressure (Δp) increased the flow rate increased. The time required toremove emboli from the chamber with respect to the irrigation andaspiration pressures and the cross sectional area used for aspiratingwas also investigated. As expected, as the aspiration cross sectionalarea increased, there was a reduction in the time required to remove theemboli which was due to the corresponding fluid flow increase. Theresults showed that by increasing the initial Δp across the system, theflow rate increased as well, but the irrigation pressure had more effecton the flow rate than the aspiration pressure. The emboli removal wasalso affected by the flow rate with a shorter time being required forremoval for a higher Δp and again, the higher irrigation pressure wasthe major factor.

There was some initial concern that pressure would build within thechamber if the configuration of the system or the change in pressure wasnot properly designed. However, in the studies performed, the pressurewithin the chamber ranged between -7.1 to 2 psig (gauge pressure where 0psig=atmospheric pressure) depending on the main catheter internaldiameter (ID) and the Δp across the system. These results indicate thatover pressurization of the chamber is not an issue in this system.

Further investigation into the fluid mechanics in the emboli containmentchamber was conducted as follows. A main catheter having an occlusionballoon on its distal end was first inserted into a 4 mm ID flexiblepolymer tube. A guidewire having a 4 mm inflatable occlusion balloon atits distal end was inserted through the main catheter and past thedistal end of the main catheter so that a 100 mm chamber was createdbetween the two balloons within the flexible tube. An irrigationcatheter was then positioned just proximal of the guidewire balloon. Themain and guidewire balloons were then inflated to isolate the chamber.

A pump was connected to an irrigation port on the irrigation catheterusing a stop cock, and a pressure gauge was connected inline with thepump output line. A 60 cc syringe was connected to an aspiration port onthe main catheter to provide aspiration pressure or vacuum. Avacuum/pressure gauge was connected inline with the aspiration line tothe syringe. A 100 ml beaker of fluid (8.5 g/L sodium chloride solutionor water) to be used in the test was then provided. The pump wasoperated until the chamber was filled with fluid and all the air was outof the irrigation and aspiration catheters.

A summary of the apparatus used in testing is shown below in Table 1:

                  TABLE 1                                                         ______________________________________                                        Test Apparatus Dimensional Breakdown                                          ______________________________________                                        Main Catheter ID/OD:   .065/.086                                              Irrigation Catheter    .038/.046                                              ID/OD:                                                                        Asp. X-sectional Area: .0017 in.sup.2                                         Chamber length:        10 cm                                                  Chamber ID:            .4 cm                                                  Chamber Volume:        1.3 cc.                                                ______________________________________                                    

With the input line to the pump in the filled beaker, the pump wasoperated and adjusted to the desired pressure. Twenty-five cc of fluidwas measured and placed into an empty beaker, and the input line to thepump was placed into the beaker. The stop cock to the aspirationcatheter was closed, and the plunger on the 60 cc syringe was pulledback until the desired vacuum was obtained. The pump was then turned on,and simultaneously, the stop cock to the aspiration port was opened anda timer was started. When the desired time had passed, the pump wasturned off and the fluid remaining in the beaker and the fluid collectedin the 60 cc syringe was measured.

A two level factorial design with two replications was used to determinethe effect irrigation pressure and aspiration vacuum had on the flowrate through the system via the 4 mm×100 mm tubular chamber (see Table2).

                  TABLE 2                                                         ______________________________________                                        Factors and levels                                                            Factor           Low Level   High Level                                       ______________________________________                                        Irrigation Pressure                                                                            5 psig      30 psig                                          Aspiration Pressure                                                                            -10 in-Hg   -25 in-Hg                                        ______________________________________                                    

The results of the testing are shown below in Tables 3 and 4.

                                      TABLE 3                                     __________________________________________________________________________    Flow Data Using a Saline Solution for Irrigation                              Initial*                                                                          Irr   Asp    δVin                                                                          δVout                                                                         δVin-δVout                                                              Time  ASP Flow Rate                        δP                                                                          Initial Press                                                                       Initial Press                                                                        mean                                                                             stdev                                                                            mean                                                                             stdev                                                                            mean                                                                             stdev                                                                            mean                                                                             stdev                                                                            mean                                                                              stdev                            (psi)                                                                             (psig)                                                                              (in-Hg, gauge)                                                                       (cc)                                                                             (cc)                                                                             (cc)                                                                             (cc)                                                                             (cc)                                                                             (cc)                                                                             (sec)                                                                            (sec)                                                                            (cc/min)                                                                          (cc/min)                         __________________________________________________________________________     9.9                                                                               5    -10    4.2                                                                              .20                                                                              4.1                                                                              .23                                                                              .2 .12                                                                              53.7                                                                             1.46                                                                             4.6 .15                              17.3                                                                               5    -25    8.3                                                                              .58                                                                              8.4                                                                              .35                                                                              -.1                                                                              .23                                                                              54.8                                                                             .37                                                                              9.2 .33                              19.9                                                                              15    -10    9.1                                                                              .12                                                                              8.8                                                                              .20                                                                              .3 .31                                                                              53.2                                                                             1.04                                                                             9.9 .41                              27.3                                                                              15    -25    10.5                                                                             .46                                                                              8.4                                                                              .53                                                                              2.1                                                                              .42                                                                              55.6                                                                             2.45                                                                             9.1 .65                              34.9                                                                              30    -10    10.1                                                                             .12                                                                              9.3                                                                              9.27                                                                             .8 .40                                                                              53.7                                                                             .58                                                                              10.4                                                                              .36                              42.3                                                                              30    -25    10.2                                                                             .40                                                                              9.1                                                                              .61                                                                              1.1                                                                              .23                                                                              53.6                                                                             .58                                                                              10.2                                                                              .57                              __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Flow Data Using Water for Irrigation                                          Initial*                                                                          Irr   Asp    δVin                                                                          δVout                                                                         δVin-δVout                                                              Time  ASP Flow Rate                        δP                                                                          Initial Press                                                                       Initial Press                                                                        mean                                                                             stdev                                                                            mean                                                                             stdev                                                                            mean                                                                             stdev                                                                            mean                                                                             stdev                                                                            mean                                                                              stdev                            (psi)                                                                             (psig)                                                                              (in-Hg, gauge)                                                                       (cc)                                                                             (cc)                                                                             (cc)                                                                             (cc)                                                                             (cc)                                                                             (cc)                                                                             (sec)                                                                            (sec)                                                                            (cc/min)                                                                          (cc/min)                         __________________________________________________________________________     9.9                                                                               5    -10    7.3                                                                              .30                                                                              6.6                                                                              .38                                                                              .7 .15                                                                              57.7                                                                             2.23                                                                             6.9 .15                              17.3                                                                               5    -25    14.4                                                                             2.09                                                                             13.4                                                                             1.43                                                                             1.0                                                                              2.15                                                                             56.1                                                                             .46                                                                              14.4                                                                              1.47                             19.9                                                                              15    -10    12.1                                                                             4.22                                                                             9.3                                                                              .58                                                                              2.8                                                                              3.64                                                                             56.0                                                                             .57                                                                              10.0                                                                              .56                              27.3                                                                              15    -25    10.5                                                                             .50                                                                              9.9                                                                              .61                                                                              .6 .53                                                                              54.6                                                                             2.81                                                                             10.9                                                                              .78                              34.9                                                                              30    -10    10.9                                                                             1.01                                                                             10.1                                                                             .50                                                                              .7 .76                                                                              55.5                                                                             3.41                                                                             11.0                                                                              .15                              42.3                                                                              30    -25    9.8                                                                              .35                                                                              10.0                                                                             .20                                                                              -2 .20                                                                              53.1                                                                             .99                                                                              11.3                                                                              .15                              __________________________________________________________________________     *Pressure equalization after max 45 sec. As δP increases, the time      to equalize increases                                                         δP is the pressure differential between the irrigation bag and the      vacuum in the aspiration syringe                                              V = volume and n = 3 unless otherwise noted                              

The irrigation pressure was varied between 5 and 30 psig with theaspiration pressure varying between -10 and -25 in-Hg. The results showthat there was little difference between the use of the saline solutionand the use of water. The lowest flow rate of 4.6 cc/min was obtainedfor a 5 psi irrigation pressure and a -10 in-Hg aspiration pressure(δp=9.9 psi). The highest flow rates were obtained when a 30 psiirrigation pressure was used with rates of 10.4 and 10.2 cc/min for anaspiration pressure of -10 (δp=34.9 psi) and -25 in-Hg (δp=42.3 psi)respectively.

The results of this two level factorial design supported the resultsobtained in earlier studies: that as the δp across the system increases,the flow rate increases exponentially.

The results were consistent with Bernoulli's equations for flow in atube in that the fluid velocity is proportional to the square root ofthe pressure differential between the two points assuming a constantfluid density and losses. When the flow rate was plotted against δp anexponential trend with an R² =0.7154, the results support theproportional relation between pressure and the fluid flow rate expressedin equation 2 (see FIG. 19).

Analysis of the data produced an extremely significant model with anadjust R² =0.994 (see Table 5). Each of the main factors as well as theinteraction between the irrigation and aspiration pressure were highlysignificant with a p<0.0000.

                  TABLE 5                                                         ______________________________________                                        Data Analysis and Model for Flow Rate (solution: saline)                      ______________________________________                                        Adjusted R.sup.2                                                                        .994                                                                Standard Error                                                                          .227                                                                Mean Abs. Error                                                                         .1278                                                               ______________________________________                                                    Coefficient                                                                              Error   Factor* p-value                                ______________________________________                                        Flow Rate (cc/min) =                                                                      8.6        ±.0654                                                          3.367      ±.1309                                                                             Irrigation                                                                            .0000                                              -2.2       ±.1309                                                                             Aspiration                                                                            .0000                                              2.37       ±.1309                                                                             Irr* Asp                                                                              .0000                                  ______________________________________                                         *Use coded values between -1 and 1 to determine predicted flow rates     

The analysis of the interaction between the irrigation and aspirationpressure showed that by using a lower aspiration pressure of -25 in-Hgthe effect of the irrigation pressure can be minimized (see FIG. 20).The increase in the flow rate between 5 and 30 psig was 10.0 cc/min foran aspiration pressure of -25 in-Hg, whereas the increase wassignificantly higher, 5.6 cc/min, when an aspiration pressure of -10in-Hg was used. Another advantage of using the lower aspiration pressurewas that it took longer for the pressure to equalize as measured by theaspiration pressure gauge thus a higher flow rate was sustained over alonger period of time.

The tubular chamber used in this study was 4 mm×100 mm which contained avolume of 1.3 cc; therefore for the worst case flow rate of 4.6 cc/min(IP=5 psig, AP=-10 in-Hg) the fluid is exchanged approximately 3.5 timestaking approximately 17 seconds for each exchange. The fluid collectionin one minute is 9.2 cc for an IP=5 psig and an AP=-25 in-Hg, whichwould flush the 1.3 cc chamber in approximately 7.5 seconds or 8 timesper minute.

This understanding of the fluid mechanics inside the emboli containmentchamber resulting from the testing described above lead to thedevelopment of the method of the present invention, which providesefficient irrigation and aspiration for removal of emboli and debrisinside the body following treatment of an occluded vessel.

Emboli Containment Methods of the Present Invention

The operation and use of the emboli containment system utilizing thecatheters of the present invention for treating occluded vessels willnow be described in connection with an occlusion formed by a stenosis ina carotid artery, as illustrated in FIGS. 18A-H. It should be noted thatthis application is merely exemplary, and that the method of the presentinvention can be used in other blood vessels in the body as well. Theword "proximal" as used herein refers to the portion of the catheterclosest to the end which remains outside the patient's body, while"distal" refers to the portion closest to the end which is inserted intothe body.

A guiding catheter (not shown) is first introduced into the patient'svasculature through an incision in the femoral artery in the patient'sgroin. The guide catheter is advanced through the artery into the aortaof the heart of the patient and into the ostium of the carotid artery tobe treated, where it remains throughout the procedure if needed.Fluoroscopy is typically used to guide the catheter and other devices tothe desired location within the patient. The devices are typicallymarked with radiopaque markings to facilitate visualization of theinsertion and positioning of the devices.

Referring now to FIG. 18A, a main catheter 410 having a distal attachedocclusive device 412, in this example an inflatable balloon, is advancedinto the ostium of the carotid artery and into the lumen 418 of thevessel 414. The main catheter 410 with the occlusive device 412 thereonis advanced until the device 412 is just proximal to the stenosis 406.The device is activated, i.e. the balloon 412 is then inflated, toocclude the vessel 414. The inner catheter, in this example a guidewire400, having an occlusive device 402, in this example an inflatableballoon, at its distal end 404 is next delivered through the maincatheter 410. The occlusive device 402 is positioned just distal to theocclusion 406. The occlusive device is activated, i.e., the balloon 402is inflated to create an isolated chamber within the vessel whichsurrounds the occlusion. The balloons 402, 412 are each progressivelyinflated until they engage the side wall of the vessel 414 to occludethe lumen 418. Preferably, the distance between the proximal end of theocclusive device on the guidewire 404 and the distal tip of theocclusive device on the main catheter 416 should be approximately 5-10cm. Advantageously, the present invention allows for the creation of atreatment and containment chamber whose length can be easily adjusted toisolate a specific area within a blood vessel. As soon as both balloons402, 412 are inflated, a working space 422 is provided between theballoons 402, 412, so that therapeutic procedures can be undertaken toremove or reduce the occlusion 406 in the space between the balloons422, without risk of unwanted particles or emboli escaping into theblood stream. The inner catheter 400 and the main catheter 410 withtheir attached distal occlusive devices 402, 412 are therefore used tocreate a chamber 422 surrounding the occlusion 406, and act to containthe emboli and debris 424 resulting from the treatment of the occlusion406 as illustrated in FIG. 18C.

Alternatively, a guide catheter or angiography catheter can first bedelivered to the site of the occlusion. The inner catheter is insertedthrough the guide or angiography catheter, and positioned within thepatient. The guide or angiography catheter is removed, and the maincatheter is inserted over the inner catheter into position proximal tothe occlusion. The occlusive device at the distal end of the maincatheter is activated, the occlusive device on the inner catheter is putinto position distal to the occlusion and activated, and the procedurecontinues as described above.

Alternatively, the main catheter can be delivered directly to a positionjust proximal to the occlusion, without use of a guide or angiographycatheter. The inner catheter is then delivered through the main catheteras described above.

In another alternative embodiment of the present invention, the innercatheter can be delivered first through the guide catheter. Theocclusive device on the distal end of the inner catheter is positioneddistal to the occlusion. The main catheter is introduced over the innercatheter and advanced into the ostium of the carotid artery and into thelumen of the vessel. The main catheter is advanced until the balloon isjust proximal to the occlusion. The intermediate catheter is thendelivered into the chamber to provide appropriate therapy. The occlusivedevices on the distal ends of the inner and main catheters areactivated, to create a treatment and isolation chamber surrounding theocclusion. This method can be used when the physician determines thatthe risk of crossing the occlusion prior to activation of the proximalocclusive device is minimal.

Referring now to FIG. 18B, once the chamber has been created around theocclusion, an intermediate catheter 420 is delivered to the site of theocclusion 406. In the example illustrated in FIGS. 18A-F, theintermediate catheter 420 is a therapy catheter having an angioplastyballoon on its distal end. The intermediate catheter 420 is delivered tothe sit, of the occlusion 406 as shown in FIG. 18B.

The term "therapy catheter" is meant to include any of a number of knowndevices used to treat an occluded vessel. For example, a cathetercarrying an inflatable or mechanically activated balloon for use inballoon angioplasty, as is used in this example, can be delivered todilate the stenosis. Thermal balloon angioplasty includes the use ofheat to "mold" the vessel to the size and shape of the angioplastyballoon. Similarly, an intravascular stent can be delivered via aballoon catheter and deployed at the site of the stenosis to keep thevessel open. Cutting, shaving, scraping, or pulverizing devices can bedelivered to excise the stenosis in a procedure known as atherectomy. Alaser or ultrasound device can also be delivered and used to ablateplaque within the vessel. Various types of rheolitic devices could beused. Various thrombolytic or other types of drugs can be deliveredlocally in high concentrations to the site of the occlusion. It is alsopossible to deliver various chemical substances or enzymes via acatheter to the site of the occlusion to dissolve the obstruction. Acombined aspiration and therapy catheter can also be used. The term"therapy catheter" encompasses these and other similar devices.

Referring now to FIG. 18D, after the balloons 402 and 412 are properlyinflated, and the therapy catheter 420 in place, therapy begins. Foremboli containment systems featuring balloon dilatation treatment, it isdesired to compress the plaque or material forming the 406 to provide alarger passageway through the vessel. Thus, a balloon angioplastycatheter 420 is positioned such that the distal end with the balloon 426thereon is at the site of the occlusion 406. When the balloon 426 hasbeen properly positioned within the 406, the balloon 426 is inflatedwith a suitable inflation medium, as for example a radiopaque liquid.The angioplasty balloon 426 can be inflated to the desired pressure tocause compression of the plaque of the occlusion 406 against thesidewall of lumen 414 by the application of appropriate inflationpressure, as shown in FIG. 18D. As in conventional angioplastyprocedures, the balloon 426 can be formed of a non-elastic relativelynon-compliant material so that appropriate pressures, such as 10-15atmospheres, can be created within the balloon to apply compressiveforces to the vessel 414 without danger of rupturing the vessel 414. Itshould be appreciated that the non-elastic capabilities can also beachieved by a composite elastic material.

After appropriate therapy has been performed and the occlusion 406 hasbeen removed or lessened using any of the methods and apparatusdescribed above, the therapy balloon 426 is deflated as illustrated inFIG. 18E. A source of irrigation fluid (not shown) is connected to theadaptor 434 located at the proximal end of the therapy catheter 420, anda source of aspiration pressure (not shown) is connected to an adaptor436 located at the proximal end of the main catheter 410, as illustratedin FIG. 18F. Preferably, the source of irrigation fluid is a bag ofnormal saline, typically used in intravenous infusion. The source ofaspiration pressure is preferably a syringe. After the source ofirrigation and aspiration are connected, irrigation and aspiration arebegun. Irrigation fluid is provided through the inner pathway betweenthe therapy catheter 420 and the guidewire 400, while aspiration isprovided through the outer pathway between the therapy catheter 420 andthe main catheter 410 as shown by the small arrows in FIG. 18F. Ofcourse it is to be understood that irrigation fluid could be providedthrough the outer pathway while aspiration is provided through the innerpathway. In either case, suitable pressures are provided to ensure thatthe change in pressure inside the chamber does not damage the vessel.The change in pressure as fluid flows into and out of the chamber shouldnot exceed about 50 psi. Suitable pressures range from approximately -10to -30 in-Hg aspiration pressure, and about 5 to 30 psig irrigationpressure. Note that these pressures are measured at the proximal end ofthe catheters.

In an alternative embodiment not shown, after therapy has been performedto remove or reduce the occlusion the therapy catheter is removed fromthe emboli containment system, and an irrigation catheter is deliveredto the emboli containment chamber. The irrigation catheter is insertedthrough the main catheter lumen. The main lumen of the irrigationcatheter can ride over the inner catheter, or the inner catheter can bepositioned in a separate lumen adjacent to the main lumen. The distalend of the irrigation catheter is positioned just proximal the distalocclusion balloon, preferably approximately 1-2 cm from the balloon. Asnoted above, the irrigation and main catheter are sized such that theirrigation catheter can pass through the main catheter lumen and theannulus or outer pathway between the main catheter lumen and theirrigation catheter is large enough to allow aspiration of the blood anddebris through it. Irrigation fluid is provided through the innerpathway between the inner catheter and the irrigation catheter.Alternatively, an aspiration catheter, a combined irrigation/aspirationcatheter, or similar debris removing device such as a rheolitic device,can be used as the intermediate catheter. In this embodiment of theinvention, the aspiration catheter is delivered in the same manner asdescribed above for the irrigation catheter. Aspiration then occursthrough the inner pathway, while irrigation is provided through theouter pathway.

Once the desired catheters are properly positioned, irrigation andaspiration are performed. The irrigation fluid and aspiration pressureare delivered in such a way as to ensure that the change of pressurewithin the chamber is below about 50 psi to avoid damaging the vessel.The irrigation fluid, preferably normal saline solution, is preferablydelivered at a pressure of from about 5 psi to about 50 psi; 5 psi ispreferred. The aspiration pressure is preferably between about -5 and-30 in-Hg, and more preferably is about -20 in-Hg. Again, thesepressures are measured from at the proximal end of the catheters. Theirrigation and aspiration can be delivered simultaneously, continuously,or delivery can be pulsed, or one can be delivered continuously whilethe other is delivered in a pulsed fashion. The user can determine thebest method of delivery to provide optimized flow, turbulence, andclearance within the chamber.

Referring again to FIG. 18F, it is preferable that the inflationpressure within the distal occlusion balloon 402 is maintained at alevel greater than the pressure in the chamber and the jet created byirrigation to avoid the leakage of fluid and debris past the distalocclusion balloon 402. Similarly, the inflation pressure in the proximalocclusion balloon 4132 should be maintained at a level greater than thepressure in the chamber and the aspiration pulsation to avoid havingfluid aspirated from behind the balloon 412 and possibly aspirating theballoon 412 itself. Again, the irrigation and aspiration pressuresprovided are such that the change in pressure during fluid flow into andout of the vessel does not damage the vessel. The change in pressure ispreferably no greater than about 50 psi.

In another embodiment of the present invention, after the therapycatheter is removed, the aspiration catheter is delivered such that itsdistal end is positioned approximately 1-2 cm from the distal occlusivedevice. The proximal occlusive device is then deactivated, to allowblood flow into the chamber. This blood flow is used as irrigation flow.The blood, acting as irrigation fluid, is aspirated together withparticles and debris through the aspiration catheter. This eliminatesthe need for a separate source of irrigation fluid. In this embodiment,it is preferred that the blood flow rate in the vessel is greater thanabout 100 cc/min, and flow rates of 60-80 cc/min are preferred. Thismethod is illustrated in FIG. 18G.

In yet another embodiment, illustrated in FIG. 18H, after the therapycatheter is removed, the proximal occlusive device is deactivated,allowing blood flow into the chamber. The blood, acting as irrigationfluid, is aspirated together with particles and debris through theopening in the main catheter. This eliminates the need for a separateaspiration catheter and a separate source of irrigation fluid, therebyreducing the time necessary to complete the procedure.

Aspiration and irrigation are continued until particles and debris 424are removed from the chamber 422, then the irrigation, aspiration, orthe therapy catheter 420, is removed. First the distal 402 and then theproximal 412 occlusion balloons are deflated, and the guidewire 400 andmain catheter 410 are removed. Finally, the guide catheter is removed,and the incision in the patient's femoral artery is closed.

Although the foregoing detailed description has described severalembodiments of the present invention, it is to be understood that theabove description is illustrative only and not limiting of the disclosedinvention. It will be appreciated that certain variations of the presentinvention may suggest themselves to those skilled in the art. Thus, thespirit and scope of this invention are to be limited only by the claimswhich follow.

What is claimed is:
 1. A catheter system for a vascular network,comprising:a hollow guidewire having a proximal end and a distal end; aninflatable balloon mounted on the distal end of the guidewire; anintermediate catheter, wherein at least a portion of said intermediatecatheter is positioned over said guidewire such that an inner fluidpathway is formed therebetween and such that the intermediate catheteris slidable to a location proximal to the balloon; and a main cathetersized to receive the intermediate catheter such that an outer fluidpathway is formed therebetween for either irrigation or aspiration, saidmain catheter having an inflatable balloon mounted on a distal end whichcooperates with the balloon on the inner catheter to form a chambertherebetween, and the main catheter having a port which is in fluidcommunication with the chamber to permit simultaneous irrigation andaspiration within the chamber; wherein the port is sized to allow thepassage only of particles between about 20 micrometers and up to about500 micrometers for the removal of said particles from said chamber; andwherein irrigation is provided at one end of the chamber and aspirationis provided at the other end of the chamber creating a pressure changewithin the chamber that does not exceed about 50 psi.
 2. The system ofclaim 1, wherein said intermediate catheter comprises an irrigationcatheter.
 3. The system of claim 1, wherein said intermediate cathetercomprises an aspiration catheter.
 4. The system of claim 1, wherein saidintermediate catheter comprises a therapy catheter.
 5. The system ofclaim 4, wherein said therapy catheter comprises a catheter selectedfrom the group consisting of a balloon angioplasty catheter, a stentdeploying catheter, an ultrasound device, and a drug delivery catheter.6. The system of claim 1, wherein said intermediate catheter comprises acatheter which can both aspirate and irrigate.
 7. The system of claim 1,wherein the inner pathway and the outer pathway each have an opening ata distal end which are approximately equal in size.
 8. The system ofclaim 1, wherein the inner pathway and the outer pathway each have anopening at a distal end of at least about 150 micrometers.
 9. The systemof claim 1, wherein the inner pathway and outer pathway comprise eachhave an opening at a distal end of at least about 500 micrometers indiameter.
 10. The system of claim 1, wherein said intermediate catheterfurther comprises a main lumen and a separate lumen adjacent said mainlumen sized to received said inner catheter slidably therein.
 11. Thesystem of claim 10, wherein said separate lumen further comprises a slitin an outside wall of said separate lumen for insertion and removal ofthe inner catheter therethrough.
 12. The system of claim 1, whereinirrigation fluid is provided through said inner pathway and aspirationpressure is provided through said outer pathway.
 13. The system of claim1, wherein the inner fluid pathway and the outer fluid pathway each havean opening at a distal end which are sized to balance fluid flow. 14.The system of claim 1, wherein the inner fluid pathway and the outerfluid pathway each have an opening at a distal end of at least about 150micrometers.
 15. A catheter system for treating a blood vessel,comprising:a hollow guidewire having a proximal end and a distal end; anocclusion device mounted on the distal end of the guidewire; anintermediate catheter, wherein at least a portion of the intermediatecatheter is positioned over the guidewire such that an inner fluidpathway is formed therebetween to permit irrigation or aspiration andsuch that the intermediate catheter is slidable along said guidewire toa location proximal to the occlusion device; and a main catheter sizedto receive the intermediate catheter such that an outer fluid pathway isformed therebetween for simultaneous irrigation or aspiration; whereinirrigation is provided through one of the fluid pathways and aspirationis provided through the other fluid pathway creating a pressure changewithin the vessel that does not exceed about 50 psi.
 16. The cathetersystem of claim 15, wherein the main catheter includes a port whichpermits simultaneous irrigation or aspiration.
 17. The catheter systemof claim 15, wherein the main catheter has an outer diameter of lessthan about 5 mm.
 18. The catheter system of claim 15, wherein the innerfluid pathway and the outer fluid pathway each have an opening at adistal end of at least about 150 micrometers.
 19. The catheter system ofclaim 15, wherein the inner fluid pathway and the outer fluid pathwayeach have an opening at a distal end of at least about 500 micrometers.20. The catheter system of claim 15, wherein the inner catheter isconstructed of nickel titanium.
 21. The catheter system of claim 15,wherein the inner catheter has an outside diameter of about 0.014inches.
 22. The catheter system of claim 15, wherein the inner fluidpathway and the outer fluid pathway each have an opening at a distal endwhich are sized to balance fluid flow.